My MacBook Pro only seems to be using half of the available RAM?

So I've recently purchased a RAM update kit (Crucial 8GB upgrade kit, 1067MHz DDR3) for my Mid-2010 MacBook Pro 13" 2.66GHz. Once the upgrade was made, I started feeling the computer running hotter: fans started kicking in earlier, and iStat Pro is telling me i'm running at around 60 degrees celsius with just Chrome and Mail open, and running in the 70s every time I did something a little bit more intensive.

I've since then been all over the web trying to find out why my MBP would be overheating like this (something I don't think it used to do before) at low CPU loads, and one of the explanations offered was that I might have purchased the wrong frequency of RAM sticks, which later it turned out I hadn't.

Anyway, so I was running a few things today (mainly facetime), at around 72 degrees celsius, after resetting both PRAM and SMC earlier today, and I opened up my activity monitor, only to find that exactly 4GB of the available 8 was free. Is this the sign that somehow one of my RAM sticks isn't functioning, or just a really crazy coincidence?? I checked in system report and both RAM banks have the status OK, so I don't know what to make of this situation at all.

By the way, I swapped out the RAM sticks and my MBP consistently ran 5 degrees C cooler, so I don't think I'm completely delusional about this (as opposed to most people).

If it's of any help, I'm running ML 10.8.2 with everything up to date.

I just opened up my whole dock to see what would happen. Surely enough, RAM usage increased past 4GB.. so it was just a weird coincidence.

But this doesn't explain why all of a sudden my CPU is running hotter. I've read terms such as "overclocking" in sentences like "in order to compensate for xyz". I can't pretened to understand this, but I don't think it's normal that my fans running at 5.7k RPM at low loads. Is there some kind of test i can run to check if any of my components are faulty, or any explanation for high CPU tempteratures at low loads?

The more stress you put on the CPU/GPU the more heat will be generated, The fans should respond to the internal temperatures generated. You can run an Apple Hardware Test that will give you information on the status of some of the internal components.

The more stress you put on the CPU/GPU the more heat will be generated, The fans should respond to the internal temperatures generated.

Yeah, what is confusing to me is the fact that I'm putting so much stress on my CPU/GPU (and thus generating so much heat) without seemingly doing much.. Maybe I'm just in denial over the fact that my 2.66 Core2Duo is outrageously outdated compared with current i5 MBP 13s.....

As for AHT, apparently it "isn't supported on this device". Is that a normal thing? (It required an internet connection, which i subsequently gave it)

In Apple Menu / About This Mac / More Info.. / Memory, you get a graphical representation of whatever the Mac sees as its memory. If both slots show up as filled and enabled, then you have what you put in and memory management is up to the OS.

Actually, just adding the additional RAM will increase the heat load on your computer. RAM uses energy and gives off heat - double the amount of RAM and you increase the heat being generated in the case.

Depends where the actual sensors are (I do not think the cpu is the actual on-die temperature in any Apple machine), and in the closed space of a MBP and the controlled airflow through it, to some extent every sensor is responding to the overall heat load. Plus the RAM sockets are near and below the cpu, I think, in terms of the layout of the logic board. Also, your cpu does have to work at least a wee bit harder as well, just because of the extra ram - more address space to index and track, larger VM page address space to monitor and so on.

Besides an intel i5 or i7 cpu running in the 60's to 80's degrees is pretty much the norm for those chips, so it is nowhere near dangerously hot (critical on-die temperature is 100C or 105C).

Great. Everything you're saying makes sense. I guess I'll just have to accept the fact that I'm running an old CPU and that it can't always keep up with the workloads its modern counterparts are dealing with easily. ^^

By the way, you mentioned the VM page. It's become quite large since I upgraded my hard drive (hovering around 350GB of theoretical max size). Is it possible to limit this somehow, making the VM page smaller and more easy to handle for the CPU? xD

VM is handled by OS X and not really something a user can easily manipulate. Note too that the VM size reported is just the address space reserved, not how much is actually in use. The size reserved is set by the OS at startup based on available RAM - it has to be done then so the kernel can setup the swap space memory registers (which are in RAM) that will be used to track pageouts if or when they ever actually get written to disk.

Once those registers are in RAM though, unless your machine is page swapping a lot, they are largely idle (and with the RAM you have, I'd bet your really are not using any of your VM anyway).

Michael Black, greetings: You said " just adding the additional RAM will increase the heat load on your computer". I cannot agree with that. Merely increasing RAM alone will have a negligible increase in heat generation from a practical perspective. Using the RAM will. Note the temperatures on my MBP as I respond to you:

Note that my MBP has 16 GB RAM and the temperatures are in essence the same as when it arrived with the original 4 GB. I would suggest use, not size is the governing parameter.

Actually, just adding the additional RAM will increase the heat load on your computer. RAM uses energy and gives off heat - double the amount of RAM and you increase the heat being generated in the case.

Not unlike adding a second light bulb in a closed box.

Sorry to disagree, but that is BS.

All the MBPs come with two SODIMM modules from factory. Both slots are always filled. The extra heat load afforded by the bigger capacity storage chips on a larger capacity SODIMM is negligible over the load already present to energize the entire circuit. And the workload on the drive (hard or SS) diminishes since there will be less pagination onto the swaparea, thus reducing the heat that component produces. My MBP hasn't paginated since last Dec., according to the Activity Monitor memory stats. And has not gone anywhere near the dread 100C threshold no matter how much load I've placed.

As for where the heat is, be sure to use the proper tools to measure. The only tool I've seen that can tell you what each one of the many heat sensors inside is detecting is Michel Bresink's free Temperature Monitor. http://www.bresink.de/osx/TemperatureMonitor.html His Hardware Monitor does likewise, together with lots of other data, but that's shareware and I don't have it.

Actually, just adding the additional RAM will increase the heat load on your computer. RAM uses energy and gives off heat - double the amount of RAM and you increase the heat being generated in the case.

Not unlike adding a second light bulb in a closed box.

Sorry to disagree, but that is BS.

All the MBPs come with two SODIMM modules from factory. Both slots are always filled. The extra heat load afforded by the bigger capacity storage chips on a larger capacity SODIMM is negligible over the load already present to energize the entire circuit. And the workload on the drive (hard or SS) diminishes since there will be less pagination onto the swaparea, thus reducing the heat that component produces. My MBP hasn't paginated since last Dec., according to the Activity Monitor memory stats. And has not gone anywhere near the dread 100C threshold no matter how much load I've placed.

As for where the heat is, be sure to use the proper tools to measure. The only tool I've seen that can tell you what each one of the many heat sensors inside is detecting is Michel Bresink's free Temperature Monitor. http://www.bresink.de/osx/TemperatureMonitor.html His Hardware Monitor does likewise, together with lots of other data, but that's shareware and I don't have it.

Not BS at all. I never said it added a large or major heat load. But the fact is, anything that uses more energy in the system is going to generate additional residual heat. Basic physics - an an 8GB SODIMM has twice the RAM of a 4GB SODIMM, and uses more energy and WILL generate more heat.

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